Process for puffing hydrophobic nylon type fibers by swelling the fibers and generating oxygen in situ



United States Patent "ice WREQEIBERS B:Y. .SWELLING; THE :EIBERSLAN D'QXYGEN N 151 U.

FRichard "Hochreuter, Rorschach, .Switz erland, assignor to FeldmuhleA.-G., Rorschach, Switzerland .N -Drawing. ApplicationAugustll, 1955Serial ,No. 527,889-

fllaims priority, application Switzerland December- 27, 1954 2 GI mS-(.Cl- :18.48)

The present invention relates to the production of aerated syntheticfibres,-, panticnlarly such fibres of the ,n lyamide, .polyes e an p lxo itr yp 'Itjis generally known, that fibers consisting ofregenstated,cellulosehave a substantially higher thermal con- .ductivityincomparison with native cellulose fibers, and @1181 the heat insulatingcapacity of garments, which are made offregenerated cellulose "fibers,is accordingly only In order to overcome thisdrawback, it has already.been, proposed to provide heat-insulating voids within the regeneratedcellulose fibers, and such methods have been reportedin the--literaturein several instances. According to one, offthosemethodsa spinningcomposition having finely divided gasbubbles suspended therein isproduced by either-adding gas evolving substancesgto the spinningsolution or by directly aerating saidsolution-with air or another gas,and then coagulating the formed dispersionduring the spinning operation.Generally the gas'is only -liberated from the gasevolving;substance'after the spinning composition emerges from thespin-neret. According toanother method, some suitable solid orliquid-substance-is added to-.:tl'1e sp-inningsolution, which substanceis subsequently dissolvedout -of the filaments, whereby fine hollowspaces are formed withinthe *fibers.

' A similar ---result canbe obtained, if the cellulose fiber is swelledin an aqueous medium, which contains unstable compounds, the latterbeingsubsequentlydecomposed under evolution of gas. However, thoseabove-mentioned procedures have-heretofore only-been applied toregenerated cellulose fibers.

It is therefore an object-of the present invention to provide ,means.facilitating the manufacture; of aerated fully-synthetic; fibers, such.as ,polyarnide polyester 01' polyaci'ylonitrile fibers which. will;have, improved heat in ulating properties,

,A, further object, of the;.inv,ention isto provide ,means enabling,.manufacture..of. aerated, fully synthetic fibers,

. .whichwill haueimproved optical ch ract ristic Still. another object.of the. invention. is, to, provide 7 means ,contribnting-totthemanufacture. of; aerated. fully synthetic or-chemical fibres,Whidtaemtfid fiberswill have unbroken surfaces.

The. ully, ynthe iafibers whi h may h reated by the .nra e io h iinention. include. polyamid fibres vof. th .pnlyhe amethxlneadiaminecadipic acid typ ch as. 1 .6 nylon, and. h poly-fimiuocaproicacid ype,.,,s.uch a nylon? polyester. fibre hs cha ,polyethy cn terep thlat .(Teryl ne), ndpnlyac ylo it ile fibr ssu h. a

A r at varie y of oth. inorganic. n san csubstances, can be .use d asswelling agent; Examples. of suitable compounds, are, chl'oroaceticacid, acetic acid, formic acid, mineral acids, saturated salt solutions,chlorarhydrate solution, phenols,. g lycols etc. Itis understood, that.the particular chosen swelling agent will depend'on the type ofsynthetic fibers used. Thus for polyamide fibers chloroacetic acid,acetic acid, formic acid and mixtures thereofhave been foundparticularlysuit- Patented Sept. 22, 1959 able. For polyester fibershydrpxlyic compounds such as phenol; canjbe conveniently used; Forjfibers ofjthe polyacrylonitrile type, e. g an ethanolic solution ofcalcium thiocyanate was foundjto be suitable.

Among the h n-co pound hi h w l. vo ve the gas or oxygen respectivelywithin the fibrillae of the treated chemical'fibers, hydrogenperoxidehas been found most suitable; however, sodium peroxide and similarperoxy compoundsare also satisfactory for the rnethod of the invention.

The employed catalyst serves to accelerate the rate of decomposition ofthe peroxides within the fibres. Suitable catalysts include heavymetals, such as silver, gold, platinum, palladium, rhodium, iridium,osmium, mercury, manganese, cobalt, iron and-copper, either. in metallicform. or in the form=of theii -salbcompounds. Aqueous solutionsofpotassiumpermanganate, of manganous salts,

such as manganous chloride and: manganous sulphate,

and of cobaltous. salts, such as cobaltous sulphateare particularlysatisfactory'forrthe purpose of the invention.

When carrying out the above-mentioned process, the fibers which may havebeen previously dried are treated either in filament form or inf'orm offabric or tissues successively with-a suitabl swelling agent, 'with, acatalyst for promotingthe decomposition of peroxides. and a]peroxy-compound, preferably hydrogen peroxide; The individualsteps ofthe process can be carried out at room temperature or alternatively, atelevated: temperature. In some cas sthe, fiber-s arficonveniently.immersed in diluted aceticacid after. the peroxide treatment for a shortperiod of. time.' By the-process Qf thfi) inventionthe gas or oxygenbubbles evolve, and voids are generatedwithin the fibrillae of thefibers.v The inflation of the fibers can be controlled as to differentdegrees by forming smaller or largerbubbles, by ernploying predeterminedconcentrationsofthereagents -or-by change .ofithe pH value of thetreatment baths. Despite the inflation of the full syntheticfiberstructurebymeans of smaller or larger bubbles, thestructureitself'and-the Wallsanclsurfacesthereof will not bedestroyed orbroken.

The chemical fibers treated in thismannerpossess a multiplicity, ofuniformly distributedfihollow spaces. The volume of the fibers istherebysubstantially increased, resulting in improved heat insulatingproperties, a lower specific gravity and a higher covering power of saidfibers. The numerous internal curved interfaces of the fibrillae furtherresult in; increased difiusion of the, refiected; light, whereby asubdued, lustre is conferred upon the fibers. In:comparison-.withrnassive fibers both; the dry and wet tenacity ofthedescribed hollow fibers is but slightly reduced and is still higher thanthe-corresponding tenacity of viscose rayon Example 1' A mpl of yl ifibes sswellcd fo m nutes in o r e a ti a i 1 s. exc ss. cetic acidi tion iscompleted. The fibers;are-thoroughly rinseduwith water and dried. Thethustreated fibersshow a considerable increased. water absorption, thelatter amounting to approximately 46% as compared with"13'% inztheuntreated material.

Example A sample of "6 nylon fibers undelustered) is swelled for 1minute in 70% aqueous chloroacetic acid,

rinsed with water and subsequently dipped into a 10% aqueous solution ofmanganous sulphate. The sample is washed for a short time with water andpulled through a 2% solution of caustic soda. The fibers are thentreated for minutes with hydrogen peroxide of 40% strength, the 6 nylon,which is soaked with the solution of the catalyst, being strongly puffedup by the decomposing hydrogen peroxide during this operation. Afterremoval from the peroxide bath the sample is washed several times withwater and dried. The fibers have now a delustered appearance, and whenthey are examined under the microscope, they show a multiplicity ofelongated bubbles or voids, particularly along the fiber axis.

Example 3 A sample of "6 nylon fibers is swelled for 1 minute in 70%aqueous chloroacetic acid, washed with water and subsequently treatedfor 2 minutes with a 2% aqueous solution of potassium permanganate.After washing out the excess catalyst, the sample is immersed for 5minutes in a aqueous sodium hydroxide solution, rinsed and dipped into abath of hydrogen peroxide of 40% strength. After 8 minutes it is removedtherefrom, washed and dried.

Example 4 A sample of 6 nylon fibers is swelled for 20 minutes in amixture of 85 parts of acetic acid and parts of formic acid. The fibersare then dipped into a 10% solution of manganous chloride inhydrochloric acid and left therein for 3 minutes. The sample is thentreated with a solution of sodium peroxide in hydrochloric acid. After 3minutes the fibers are washed with cold water, centrifuged and dried.The fibers show big spherical bubbles or voids.

Example 5 A sample of 66 nylon fibers is swelled for 1 minute in amixture of 35 parts of formic acid and 65 parts of acetic acid. Afterremoval of the excess swelling agent, the fibers are treated for 2minutes with a 1% aqueous solution of potassium permanganate.

The sample is then shortly washed with water, treated for 3 minutes witha 10% aqueous sodium hydroxide solution, washed again with water andfinally dipped for 5 minutes into a bath containing hydrogen peroxide of40% strength. It is then rinsed and dried.

Example 6 A 2 gm. sample of 66 nylon is swelled for 1 minute in amixture of 35 parts of formic acid and 65 parts of acetic acid. Afterremoval of the excess swelling agent, the fibers are treated for 2minutes with a 10% aqueous solution of manganous sulphate. After thefibers have been washed for a short time with water, they are immersedfor 3 minutes into a 10% solution of caustic soda, washed again withwater and finally dipped for 5 minutes into hydrogen peroxide of 30%strength. The excess hydrogen peroxide is thoroughly washed out withwater, and the sample is dried at 60 C. The fibers show a grainedappearance and are greatly interspersed with fusiform voids.

Example 7 A hank (11 g.) of 66 nylon is swelled for 2 minutes in 200 cc.of glacial acetic acid. The excess swelling agent is then squeezed outand the hank is dipped into 300 cc. of a 0.1% aqueous potassiumpermanganate solution. After seconds it is removed therefrom, rinsed fora short time with water and immersed for 3 minutes into a bathcontaining 250 cc. of a 5% sodium hydroxide solution. The hank issubsequently thoroughly washed, squeezed out and treated with 300 cc. ofhydrogen peroxide of 40% strength. After 10 minutes the hank isthoroughly washed with water and dried. After the treatment theindividual fibers are greatly interspersed Example 8 A sample of 6 nylonfibers (undelustered) is swelled for Z'min'utes in glacial acetic acid.-The excess swelling agent is then squeezed out and the fibers areimmersed for 10 minutes in a 10% aqueous solution of cobaltous sulphate.The fibers are then placed for 3 minutes in a 2% solution of causticsoda, washed with water and treated with hydrogen peroxide 'of 35%strength. The vigorous reaction, which sets in immediately, subsidesafter 3 minutes, whereupon the sample is removed from the bath, rinsedseveral times with water, freed from adhering water in the centrifugeand dried. The individual fibers have a delustered appearance which isdue to the many very fine bubbles or voids.

Example 9 A 6 nylon fabric is swelled for 5 minutes in a mixture of 15parts of concentrated formic acid and parts of glacial acetic acid. Itis then freed from excess swelling agent and immersed for 2 minutes in a1% aqueous solution of potassium permanganate. After shortly washing thepiece of fabric with water, it is dipped for 5 minutes in to a 10%aqueous solution of sodium hydroxide, washed, centrifuged and finallytreated with hydrogen peroxide of 40% strength. After 3 minutes thefabric is removed from the hydrogen peroxide bath, is placed for 2minutes in acetic acid of 10% strength, whereby it assumes a pure whiteappearance. It is then rinsed with water and dried.

Example 10 A sample of Terylene fibers is swelled in phenol for a fewminutes at a temperature of about 50 C. The excess swelling agent isthen washed out with acetone and the fibers are dipped for 5 minutesinto a 1% aqueous solution of potassium permanganate. The sample iscentrifuged, placed for 2 minutes in a 2% solution of caustic soda andsubsequently in hydrogen peroxide of 35% strength. When the reaction hassubsided, the fibers are washed several times with water and dried. Thevoids within the fibers, which are generated by the above treatment, canbe easily observed under the microscope.

Example 11 A sample of Orlon fibers is swelled for 3 minutes in asaturated ethanolic solution of calcium thiocyanate and then shortlyWashed with water.

The fibers are subsequently placed into a 4% ho aqueous solution ofpotassium permanganate, rinsed again with water and pulled through a 5%solution of caustic soda. The sample is again washed with Water and thentreated with hydrogen peroxide of 40% strength, which has been warmed to70 C. The treatment is continued for 10 minutes, whereupon the fibersare rinsed and dried.

Various changes and modifications may be made without departing from thespirit and scope of the present invention and it is intended that suchobvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, What is claimed as new and desiredto be secured by Letters Patent, is:

1. A method of manufacture of aerated synthetic hydrophobic polyamidefibres of polyhexamethyleneadipamide and poly 5 aminocaproic acid,comprising the steps of treating said fibres for between 1 minute toabout 20 minutes with an aqueous solution containing a swelling agent,said swelling agent consisting of at least one member of the groupconsisting of acetic acid, chloroacetic acid and formic acid, washingsaid fibres to remove any excess swelling agent therefrom, treating saidfibres with an oxygen generating catalyst consisting of approximately a1% aqueous solution of potassium permanganate for about 1 minute untilsaid fibres show an intense violet color, washing said fibres with wateruntil the fibres are a pale rose color, immersing the fibres in asolution of about 40% hydrogen peroxide for about 5 minutes until saidhydrogen peroxide is decomposed under the influence of said catalystevolving gas bubbles inflating said fibres without breaking the wallsand surfaces of said fibres and thus creating voids in said fibres.

2. A method of manufacture of aerated synthetic hydrophobic polyamidefibres of polyhexamethyleneadipamide and poly 5 aminocaproic acid,comprising the steps of treating said fibres for between 1 minute toabout 20 minutes with an aqueous solution containing a swelling agent,said swelling agent consisting of at least one member of the groupconsisting of acetic acid, chloroacetic acid and formic acid, washingsaid fibres to remove any excess swelling agent therefrom, treating saidfibres for between 1 minute to about minutes in a solution containingabout 0.1 to 10% of an oxygen generating catalyst selected from thegroup consisting of permanganates, manganous salts and cobaltous salts,and immersing said fibres for up to about 3 to 10 minutes in a solutionof about to concentration of a peroxide compound selected from the groupconsisting of sodium peroxide and hydrogen peroxide, until said peroxidecompound is decomposed under the influence of said catalyst evolving gasbubbles inflating said fibres without breaking the walls and surfaces ofsaid fibres and thus creating voids in said fibres.

References Cited in the file of this patent UNITED STATES PATENTS2,218,385 Schulze Oct. 15, 1940 FOREIGN PATENTS 244,446 Great BritainMar. 24, 1927 299,710 Great Britain Jan. 27, 1930 1,032,715 France Apr.1, 1953 1,071,702 France Mar. 10, 1954 OTHER REFERENCES Rayon andSynthetic Textiles, May 1950, page 91.

1. A METHOD OF MANUFACTURE OF AERATED SYNTHETIC HYDROPHOBIC POLYAMIDEFIBRES OF POLYHEXAMETHYLENEADIPAMIDE AND POLY 5 AMINOCAPROIC ACID,COMPRISING THE STEPS OF TREATING SAID FIBRES FOR BETWEEN 1 MINUTE TOABOUT 20 MINUTES WITH AN AQUEOUS SOLUTION CONTAINING A SWELLING AGENT,SAID SWELLING AGENT CONSISTING OF AT LEAST ONE MEMBER OF THE GROUPCONSISTING OF ACETIC ACID, CHLOROACETIC ACID AND FORMIC ACID, WASHINGSAID FIBRES TO REMOVE ANY EXCESS SWELLING AGENT THEREFROM, TREATING SAIDFIBRES WITH AN OXYGEN GENERATING CATALYST CONSISTING OF APPROXIMATELY A1% AQUEOUS SOLUTION OF POTASSIUM PERMANGANATE FOR ABOUT 1 MINUTE UNTILSAID FIBRES SHOW AN INTENSE VIOLET COLOR, WASHING SAID FIBRES WITH WATERUNTIL THE FIBRES ARE A POLE ROSE COLOR, IMMERSING THE FIBRES IN ASOLUTION OF ABOUT 40% HYDROGEN PEROXIDE FOR ABOUT 5 MINUTES UNTIL SAIDHYDROGEN PEROXIDE IS DECOMPOSED UNDER THE INFLUENCE OF SAID CATALYSTEVOLVING GAS BUBBLES INFLATING SAID FIBRES WITHOUT BREAKING THE WALLSAND SURFACES OF SAID FIBRES AND THUS CREATING VOIDS IN SAID FIBRES.